Heavy-duty air circuit breaker



Jan. 1, 1952 Filed Jan. '7, 1950 J. A. FAVRE 2,581,181

HEAVY-DUTY AIR CIRCUIT BREAKER 2 Sl- EETS-SHEET 1 Inventor: Johrw A.Favre,

His Att or-ne Jan. 1, 1952 J. A. FAVRE HEAVY-DUTY AIR CIRCUIT BREAKER 2SHEETSSHEET 2 Filed Jan. 7, 1950 M/Sl/L 177700 5 5 3 W M m a 0 v 7 M U ZIO I m 4 w l l0 8 J O Inventor: John A Favr-e,

9 His Attornel Patented Jan. 1, 1952 HEAVY-DUTY Am CIRCUIT BREAKER JohnA. Fa re, Drexel, Pa., alsignor to General Electric Company, acorporation of New York Application January 1, 1950, Serial No. 137,411-

The invention relates to circuit breakers, particularlyair circuitbreakers, and the principal object is to provide an improved separatelyarticulated compound sequential toggle actuated arcing and main contactform of heavy-duty air circuit breaker capable of closing onexceptionally large momentary load currents and having 9,ourrent-interrupting capacity of the same magnitude, for example, onehundred thousand amperes. With such large momentary currents carriedduring the closing and opening of the arcing and main contacts of thebreaker, severe sparking and "blow-oils of a destructive and explosivecharacter are likely to occur unless sufilcient wiping pressure as wellas successive actuation of these contacts are very accurately producedin properly timed sequence. Thus insuilicient arcing contact wipingpressure at the instant the main contacts engage or disengage may result.in the relatively large current becoming highly concentrated in one ormore minute conductive paths between the main contacts, therebyproducing such a highconcentration of the electrical 14 Claims. (Cl.200-153) A further object is to utilize the heavy electrodynamic forcesof the main and arcing contact current loops for quickly acceleratingthe joint wiping movement of the separately articulated maincurrent-carrying contacts as well as for maintaining the requiredcontact pressure therebetween until the actual separation thereof occursbefore the arcing contact pressure sequentially decreases and therebysecure as much speed and contact pressure as possible in the opening ofthe breaker under heavy overloads to minimize sparking and "blowoffs andreduce the possibilities of "restriking in interrupting currents oflarge magnitude.

Another object is to provide an improved compound sequential togglelinkage operable in closing the breaker to quickly eil'ect wiping jointmovement of the separatlyarticulated arcing contacts against normalspring ,4318881116 and maintain substantially uniform thenbrmal springenergy that immediate volatilization of the main contact material occurswith explosive blow-off force. Similar results are likely to occur incase of an untimely or premature decrease in the main contact wipingpressure before the actual separation thereof occurs or in case theseparating speed thereof is insufficient to prevent restrike upon arapid sequential separation of the arcing contacts.

Hence, a particular object is to provide an improved positive sequentialtiming form of separately articulated heavy-duty arcing and main contactcompound toggle wiping and actuating linkage capable of establishing andmaintaining -the required values of wiping pressure therebetween inproper relation with their sequential closing and opening at thecritical times necessary-to overcome the severe sparking and destructiveblowofls to which these contacts ordinarily are subjected in suchheavy-duty service. Another object is to provide an improved com'- poundsequential toggle wiping and actuating linkage for the separatelyarticulated contacts that will substantially counterbalance orneutralize the heavy electrodynamic forces of the arcing and maincontact loops so as to reduce the reaction thereof on the closingmechanism when the breaker is closed on a heavy fault. This materiallyfacilitates a successful closing operation against the normal contactwiping sprin forces by means of a stored energy device or other operatorhaving a limited maximum closing power.

pressure therebetween both during the sequential closing wipingengagement of the main current-carrying contacts against normal springpressure as well as during the reverse joint wiping movement of the maincontacts until after the accelerated separation thereof occurs in theopening of the breaker. In this way separate and successive wipinengagement and disengagement of the arcing and main contacts ispositively .,obtained in reverse sequence.

Another object is to provide an improved double latch type of trip-freepower-amplifying circuit breaker operating toggle mechanism having alatched-in centrally fulcrumed closing toggle lever biased open andprovided with a releasable fulcrum lever having a separate latchcontrolled by a sensitive overload current-responsive means so as tooperate in conjunction with the heavy electrodynamic force of both themain and arcing contact electrodynamic loops to effect the rapid openingof the breaker. Further objects and advantages of the invention willappear in the following description of the accompanying drawing in whichFig. 1 shows the improved separately articulated arcing and main contactstructure of the heavy-duty circuit breaker in the closed positionprovided with the improved compound sequential toggle wiping andactuating linkage of the present invention and Fig. 2 shows the relativepositions of the parts in the open position of the circuit breaker.

As shown, the circuit breaker indicated generally by the referencecharacter 9 is provided with an upper suitably insulatedcurrent-conducin'g terminal stud I 0 having a main contact ll pins l2and l8are held in current-conducting relation with their respectivebearing notches by means of the holding bar 2|! that is secured to theconductor stud i by screw 2|. The articulated main contact II isprovided with a wiping biasing spring '23 .for biasing the main contactI I in. one direction to the position wherein stop 24 engages with aninsulating shoulder 25. Similarly the arcing contact l5'is provided withalink 58 also is provided at the other end thereof with a separatecompression toggle link connection with the arcing contact 45 comprisingthe shorter link 55 that is connected at one end to the tension link 58by means of the oflset pin 55 and the other end to the arcing contact 45by means of pin 51 so as to be moved in the proper sequence toward andaway from force amplifying alignment with the tension link .58in'closing and opening. the circuit breaker. The main tension link 50 isshown provided with an inside-ting I crossarm 68 that may serve tointerconnect the wiping biasing spring 21 operating on the pin 28 tobias in the same direction-the tail 29 of contact I into engagement withthe insulating stop 7 88. If desired, suitable flexible braid 3| may beprovided for avoiding pitting of the main con- .tact bearing pin l2during heavy faults and a similar flexible braid 82 may be provided for.the arcing-contact bearing pin I|i for the same purpose. a

-'The circuit breaker 9 likewise is provided-with a second suitablyinsulated current-conducting terminal stud 83 that is electricallyconnected to one end-of the single turn magnetizing coil '34 for {theoverload tripping device 35 which may be of .any usual type; Theother-end of coil 34 is con- -nected to the current-conductor 36 onwhich is pivotally mounted the second separately articu- 'lated maincontact 31 by means of the conducting pivot pin 38 which is heldinconducting engagement with the'bearing notch 39 by means of --aconducting bar 4|! that is secured to the conductor 35 by means of thescrewjl In this way the two main contacts and 31 are separatelyarticulated for joint wiping movement in abutting engagement in onedirection to compress the biasing spring 28 with the facings 42 ofspecial contact material interposed therebetween. The second separatelyarticulated arcing contact 45 is mechanically and electrically connecteddirectly to the-main contact 31 by means of pivot pin 4-6 and is thussupported forjoint movement with the separately articulated arcingcontact |5 in abutting-wiping engagement in the same direction tocompress the biasing spring 21 with the facings 41 of special contactmaterial interposed therebetween. Thus, the arcing contacts l5 and 45are jointly movable in the same direction as the main contacts H and 31;Any suitable form of arc quencher or chute, 'not shown', may be providedfor extinguishingthe are between the arcing contacts l5 and 45.

inorder to accurately produce the properly timed sequential engagementand disengagement of the separately articulated pairs of arcingconitacts l5 and 45 and maincontacts' ll and3l with sufficient wipingcontact pressure therebetween, an improved form of compound sequentialtoggle linkage indicated generally by the reference character 48 isprovided. This linkage 48 comprises a main tension link 5|! 'journaledat one end on the fLked pivot pin 5| to swing the other end thereof in adirection transverse the direction of joint movement of the contacts andhaving a compression toggle link 52'connected to'the other end thereofby means of the pin 53 with the other end-or the link 52 connected tothe main contact 81 by means of pin 54 so as to be moved toward andawayvfrom force amplifying alignment with the tension link 58 in closingand opening'the circuit breaker. The main tension =and-toggle links ofeach pole substantially the same as shown in the drawing.

inorder to obtain a further force amplifying toggle action in closingthe breaker 8, the other end of the main tension link 50 is connected bymeans of the operating toggle link 6| with a bell crank closing member52 that is iournaled-intermediate its ends on the pivot pin '68 carriedintermediate the ends of areleasable fulcrum lever .64 that is joumaledon a fixed bearing pinat one. end; The other end of the releasablefulcrum lever-84 is provided'with a roller 65 for engagement with therounded end of .a trip prop. .51. This trip prop 61 is pivoted on thefixedpin." and is biased by spring 69 into engagement-with the stop 18in a position wherein the thrustfrom the roller 86" tends to move theprop 51 a ainst the bias of the spring 68. For holdin the pm currentflows through the coil 34 for the required The circuit breaker 9 isshown closed, in Fig. i, with the pair of main contacts I I and 31 inabutting wiping engagement and the shunting pair of arcing contacts l5and 45 also in abuttim wiping engagement and the bell crank operatinglever 62 is held in its closing position by the engagement of the latchwith the pin 8| carried adjacent the free end of the bell crank lever52. The'l'atch 80 is pivoted on the fixed pin 22 and'is biasedintoengagement with the pinli' by. the biasing spring 83. Suitable openingbiasing springs are connected between the pivot pin 58 on the maintensionlink 50 and-a fixed supporting member 85 so asto exert a strongbias tending to rotate the main tension link 58 about its fixed pivotalsupporting pin 5| and bodily move the bell crank 52 and the releasablefulcrum relatively lightresetting spring "88 'and thereby lower thepivot pin 83 suflicientlyto releaseithe pin 8| from engagement with thelatch 88 thereby freeing the bell crank 82' for quick Imitation underthe bias of the 0penin8-springs u; As soon as this occurs, therelatively light biasing spring 08 is then free to automatically resetthe lever .4 into its position in which it is shown and thereby carrythe bell crank lever 62 into its circuit breaker opening pofltion shownin Fig. 2 with the other parts of the circuit breaker mechanism alsooccupying their respective open positions in which they are shown.

In accordance with the present invention, when the circuit breakerlsopened by the sequential togglelinkage 48 in the manner Justdescribed, the first contact actuation produced is the joint wipingmovement of the two separately articulated main contacts II and 51. Dueto the heavy overload current flow therethrough, a heavy electrodynamicforce is exerted on each of these contacts tending to drive them to theleft and this force performs two functions. First, it accelerates theJoint wiping movement of the two main contacts I l' and 31 until thelimit of motion of the contact II is reached wherein the stop 24 engagestheshoulder 25. The second function performed by the magnetic force isin augmenting the force of the biasing spring 23 in maintaining abuttingwiping engagement between the contact facings 42 during the. jointwiping movement of the main contacts. This serves to minimize sparking,and blow-offs" by maintaining the required pressure between these maincontacts until the quick separation thereof occurs as contact II issuddenly stopped by the engagement of pin 24 with shoulder 25.

During such accelerated joint opening wiping movement of the maincontacts II and 31, the arcing contacts [5 and 45 are mechanicallymaintained substantially at rest and consequently a substantiallyuniform contact pressure is maintained therebetween by the biasing forceof the wiping spring 21. Thus the breaker operating linkage 48 includingthe main tension link 50 and the separate sequential toggle links 52 and55 insures, in conjunction with the pivotal mounting of the arcingcontact 45 on the main pivotally mounted contact II, that substantiallyno opening wiping movement of the arcing contacts can occur during thejoint opening wiping movement of the main contacts as only a slightvertical sliding relative movement between the arcing contacts l5 and 45is produced due to the compound sequential toggle pivot pins 56, 51, 46and 3| being maintained in substantially the same alignment as shownuntil after the quick separation of the main contacts H' and 31 isaccomplished. Thus upon counterclockwise rotation of the main tensionlink 50 about its pivot pin 5| to open the breaker 9, the toggle link 52rotates the main contact 31 about its pivot pin 35 to effect theacceleraed joint wiping movement of the main contacts 31 and H until thepivotal movement of contact II is suddenly stopped by 60 the engagementof stop 24 with the insulating shoulder 25 to produce suddendisengagement of the main contacts. During such accelerated joint wipingmovement and sudden separation of the main contacts II and 31, thepivotal mounting of the arcing contact 45 on the main contact 31 bymeans of the conducting pin 46 and the toggle connection of the arcingcontact 45 with the main tension link 50 by means of the separate togglelink 55 serves to produce only movement of the lower end of contact 45while maintaining the upper end thereof at rest in firm wipingengagement with the arcing contact l5 until after the separation of themain contacts I l and 31 occurs. Thereupon the compound seend 93 of thebell crank 62.

quential toggle mechanism operates to effect joint wiping movement ofthe contact l5 along with the contact 45 until the tail 29 of contact 15engages with the insulating stop 30 to thereby produce sudden separationof the arcing contacts 15 and 45. Thereupon, the arcing contact 45 israpidly carried to its fully open position in which it is shown by thedotted lines.

During the joint wiping movement of the arcing contacts l5 and 45, theelectrodynamic forces on contact 15 are substantially counterbalanced orneutralized due to the reverse loop structure. Thus, the electrodynamicloop force set up by the current flow through contacts I 5 and 45 isopposed by the electrodynamic loop force setup by the current flowthrough contact i5 and the opposite portion of the current-conductingterminal stud ID on which the contact I5 is pivotally mounted by thecurrent-conducting pin It.

Upon opening of the breaker 9, the releasable fulcrum lever 64 isautomatically reset by spring 88 and likewise the prop 61 isautomatically reset into engagement with the roller 66 by the spring 69with the latch 'H', the trip finger 14 and also theprojecting finger 16of the overload current-responsive trip mechanism 35 all returned totheir initial holding'position as shown in the drawing and with theother parts of the breaker in their respective positions indicated bythe dotted lines.

In order to reclose the breaker, the bell crank closing member 62 mustbe operated to return the pin 8| into engagement with the latch 80.Although any suitable operating means may be employed for this purpose,the improved circuit breaker 9 shown in the drawing is particularlyadapted for closing operation by the improved form of stored energymechanism 19 that is more fully described and claimed in my co-pendingapplication, Serial No. 196,075, filed November 16, 1950. As indicatedin the drawing, this improved mechanism is provided with a closing arm90 fixed on an operating shaft 9| and carrying a roller 92 for cammingengagement with the free The operating shaft 5| also has fixed thereonan actuating cam member 95 that is connected by the pivotal saddle 96with a powerful compression spring 91 in which sufllcient energy may bestored to effect the closing of the circuit breaker. The energy isimparted to the compression spring 91 by rotating the cam member 95 tothe position in which it is shown by means of the roller 98 carried onthe arm 99 that is fixed to a motor-driven shaft I 00 provided with theimproved powerful gear reduction and trip-'free overrunning clutchmechanism more fully described and claimed in my abovementionedco-pending application.

With sumcient closing energy stored in the powerful compression spring51 as shown, all that is necessary for closure of the breaker is toeffect rotation of the arm 99 from its dead-center position in which itis shown. Thereupon the powerful force of the compression spring 51 be-7 end 53 of the bell crank 62 to return the pin 5| into engagement withthe latch 80 and thereby effect the reclosure of the circuit breakers.The stored energy closing mechanism thereupon returns to its initialposition in which it is shown wherein 'suillcient energy is againstoredv in the Iii-5814181 powerful compression spring 8.1 to effect thenext re'closure of the breaker.

-In case the circuit breaker 9 should be closed on a heavy fault duringthe operation of the stored energy closing mechanism,'trip-free actionis obtained due to the release of the prop 61 thereby releasing thefulcrum lever 64 and permitting the opening of the breaker to beaccomplished 'in substantially the same way as previously describedexcept that the upturned end ll of the bell crank 62 will remain inengagement with roller 92 until the stored energy mechanism I! isreturned to its'initial position which occurs immediately after thebreaker is opened.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

1. A circuit breaker having in combination, a

' pair-of separately articulated abutting main contacts jointly movablein one direction, a pair of separately articulated abutting arcingcontacts jointly movable in one direction, and operating mechanismhaving a tension link pivotally supported at one end to swing the otherend in a direction transverse the direction of joint movement of thecontacts and provided at the other end with sequential compressiontoggle links having separate pivotal connections with one of each pairof contacts for effecting separate and successive wiping disengagementand engagement of said pairs of contacts in reverse sequence as thecompression links successively move away from and toward forceamplifying alignment with the tension link.

2. A circuit breaker having in'combination, cooperating pairs ofseparately articulated abutting arcing and main contacts separatelymovable in wiping relation in the same direction, means nor.- mallybiasing one contact of each pair for joint wiping movement with theother contact within a limited range, and operating mechanism having atension link pivotally supported at one end to swing the other end in adirection transverse the direction of joint movement of the contacts inwiping relation and provided at the other end with sequentialcompression link connections with the other contacts of each pair forsubstantially separately operating each other contact through the wipingrange of the corresponding one contact as the compression linkconnections move toward and away from force amplifying alignment withthe tension link in closing and opening the breaker.

3. A, circuit breaker having in combination, cooperating pairs ofseparately articulated abutting arcing and main contacts separatelymovable in wiping relation inthe same direction, separate means normallybiasing one contact of-each pair for joint wiping movement with theother contact, means for pivotally mounting the other of the arcingcontacts on the other of the main contacts and operating mechanismincluding a tension link pivotally supported at one end to swing theother end in a direction transverse the direc-v tion of joint movementof the contacts in wiping relationand having at the other end thereofseparate toggle link connections with the other contacts of, each pairoffset for maintaining a substantially uniform wiping contact' pressurebetween the pair of arcing contacts before, after, and during the wipingengagement of the pair of main contacts.

4. A circuit breaker having in combination a pair of spaced apartcurrent conductors having separately movable inner and outer arcing andinner and outer main contacts articulated in looped spaced relationtherewith for'electrodynamically biasingtheinner main contactintbengagement with the outer main contact, separate means biasing eachinner contact for joint wiping movement with the outer contact through alimited range, and sequential linkage mecha-- nism interconnecting theouter contacts for effecting substantially separate movement of theouter arcing and main contacts each way through the limited range ofjoint wiping movement with the corresponding inner contacts.

5. A circuit breaker having in combination, separately movable inner andouter main and inner and outer arcing contacts having pivotal mountingand conducting connections for electrodynamically biasing the inner maincontact for joint movement in wiping engagement with the outer maincontact and having the outer arcing-contact pivotally mounted on theouter maincon-- contact for joint wiping movement with the outercontact, and sequential linkage mechanism iiieluding a tension linkpivotally supported at one end and provided with sequential offsetcompression links of different lengths at the other end forinterconnecting the outer contacts to maintain'a predeterminedsiibstantially uniform contact pressure between the arcing contactsduring the wiping engagement and disengagement of the main contacts. I

6. A circuit brea er having in combination, separately'movablebutting-inner and outer main and inner and outer arcing contactshavingpivotal mounting and conducting connections in looped spaced relationfor electrodyna'mically biasing the inner main contact for jointmovement in abutting wiping engagement with the outer contact,separate'means normally biasing each inner contact for joint wiping movement withthe abutting outer contact, stop means limiting the biased movement ofeach inner contact, and compound toggle operating means having a tensionlink pivotally supported at one end and provided at the other end withseparate compression toggle links of different lengths connected withthe outer contacts for separately holding the arcing andmain contacts inwiping current-conducting engagement against the biasing forces exertedthereon and for effecting sequential disengagement of the outer contactsfrom the inner contacts at the limits of the biased movement thereof. 7I

7. A circuit breaker having in combination a pair of main contactsseparately pivoted for Joint wiping movement in one direction, a pair ofarcfing contacts separately pivoted for joint wiping movement in thesame direction, one of the arcin contacts being pivotally mounted on oneof the main contacts, and operating mechanism having a tension linkpivotally supported atone end to swing the other end thereof in a.direction transverse the direction of joint wiping movement of thecontacts and provided at the other F end thereof with separate togglelink connections of different lengths with the one arcing contact andthe one main contact offset for effecting separate and successive wipingdisengagement and engagement 'of said pairs of contacts in reversesequence. A

8. A circuit breaker-having in combination, a fixed conductor having "anarcing and a main contact separately pivoted thereon in conductingrelation therewith, 'a' second fixed conductor having a second maincontact pivoted thereon in con 76 ducting relation therewith forabutting wiping tact, separate'means normally biasing each innerengagement with the first pivoted main contact in electrodynamic loopedrelation with the conductors to increase the wiping pressure between themain contacts, a second arcing contact pivotally mounted on the secondmain contact in conducting relation therewith for abutting wipingengagement with the first arcing contact, and operatin mechanism havinga tension link pivotally supported at one end and provided at the otherend with separate compression toggle link connections of difierentlengths with the second arcing and second main contacts for effectingsequential engagement and disengagement thereof with the correspondingfirst arcing and main contacts in reverse sequence.

9. A circuit breaker having in combination, a first movable main contacthaving a separately movable arcing contact, and each having biasingmeans for eflecting separate wiping movement thereof in a limited rangeextending in the same direction, a second main contact pivotally mountedadjacent one end for joint wiping movement with the first main contact,a second arcing contact having one end thereof pivotally mountedintermediate the ends of the second main contact for joint wipingmovement with the first arcing contact, and operating mechanismincluding a tension link pivotally mounted adjacent one end to swing theother end thereof in a directiontransverse the direction of the limitedranges and havin separate compression toggle links of different lengthsoffset for interconnecting the other end thereof with the second maincontact and the second arcing contact to effect separate and successivewiping engagement and disengagement thereof with the corresponding firstcontacts in reverse sequence as the compression links successively movetoward and away from force amplifying alignment with the tension link inclosing and opening the circuit breaker.

10. A circuit breaker having in combination, a pair of main contactsseparately pivoted in alignment for Joint wiping movement in onedirection, a pair of arcing contacts separately pivoted in alignment forjoint wiping movement in the same direction, one of the arcing contactsbeing pivotally mounted on one of the main contacts, a pivotally mountedtension link having one end movable in a direction transverse thedirection of joint wiping movement of the contacts and having separatecompression toggle links of different lengths connected between the oneend thereof and the one arcing contact and the one main contact foreffecting separate and successive wiping disengagement and engagement ofsaid pairs of contacts in reverse sequence upon predeterr-ined reverseangular moverrents of they tension link in said transverse direction,and means including a toggle mechanism for effecting said predeterminedreverse angular movement of the tension link in said transversedirection to close and open the breaker. v

11. A circuit breaker having in combination, a centrally fulcrumedclosing lever provided with a releasable fulcrum lever pivoted at oneend and having overload current-responsive releasable holding meansengaging the other end thereof, a contact mechanism operativelyconnected with one end of the operating lever to close the contacts uponmovement of the closing lever from one position to another position andprovided with biasing means for opening the contacts upon response ofthe current-responsive holding means 10 to release the fullcrum lever,and a latch engageable with the other end of the closing lever forholding the closing lever in said other position against the openingbias of the contact mechanism.

12. A circuit breaker having in combination, a centrally fulcrumed mainoperating lever provided with a releasable fulcrum lever pivoted at oneend and having overload current-responsive releasable holding meansengaging the other end thereof, a sequential arcing and main contacttoggle mechanism having a toggle link connection with one end of themain operating lever to close the contacts sequentially upon movement ofthe main operating lever from one position to another position andprovided with a biasing spring for opening the contacts sequentiallyupon response of the current-responsive holding means to release thefulcrum lever, and a latch engageable with the other end of the mainoperating lever for holding the main operating lever in said otherposition against the bias of the spring.

13. A circuit breaker having in combination, an operating bell crankprovided with a releasable fulcrum lever pivoted at one end and havingoverload current-responsive releasable holding means engaging the otherend thereof, switching means having separate toggle operated main andarcing contacts provided with a common tension link having anintermediate toggle link connection with one end of the bell crank toclose the contacts upon movement of the bell crank from one position toanother position and provided with biasing means for opening thecontacts upon response of the currentresponsive holding means to releasethe fulcrum lever, a latch engageable with the other end of the bellcrank for holding the crank in said other position and closing mechanismhaving a member engageable with the other end of the bell crank toeffect movement thereof from the one position to the other position.

14. A circuit breaker having in combination, an operating bell crankprovided with a releasable fulcrum lever pivoted at one end and havingoverload current-responsive releasable holding means provided with amovable prop for engaging the other end thereof when the current isbelow a predetermined value, switching means having sequential toggleoperating main and arcing contacts operatively connected with one end ofthe bell crank to be closed upon movement of the bell crank from oneposition to another position and provided with biasing means for openingthe contacts upon response of the current-responsive holding means torelease the prop from the other end of the fulcrum lever, a latchengageable with the other end of the bell crank for holding the crank insaid other position and releasable upon the resulting movement of thebell crank upon release of the prop, and means biasing the fulcrum leverto return into engagement with the prop after the contacts are opened.

JOHN A. FAVRE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Loguin Oct. 27, 1914

